Is it leaking fluid? Brembo are pain(all be it great kit),they only seem to do replacement parts for there old Master cylinders,and there doesn't seem to be any after market parts available.Only thing i can think of,is eBay or a breakers for a good second hand one if it needs replacing and you don't want to pay new prices. Good Luck

Brembo Clutch Master cylinder.
The first link below implies that you you might be able to get suitable seals from KTM. It's talking about Brembo brake seals but maybe you can find a KTM with the same clutch cylinder.

Not sure about the newer KTMs,
but the hydraulic clutch master cylinders and slave cylinders on KTMs used to be Magura (make mountain bike stuff too and got long association with KTM and other Euro dirt bike makers) anyway, they use a mineral fluid in theirs rather than conventional brake and clutch fluid, so may not be compatible with Brembo stuff. Maybe the Aprilia forums might shed some light on the prob, and solutions? hope so